Solid-state imaging element and electronic device

ABSTRACT

To provide a solid-state imaging element capable of further improving reliability. Provided is a solid-state imaging element including at least a first photoelectric conversion section, and a semiconductor substrate in which a second photoelectric conversion section is formed, in this order from a light incidence side, in which the first photoelectric conversion section includes at least a first electrode, a photoelectric conversion layer, a first oxide semiconductor layer, a second oxide semiconductor layer, and a second electrode in this order, and a film density of the first oxide semiconductor layer is higher than a film density of the second oxide semiconductor layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 17/260,880, filed Jan. 15, 2021, which is anational stage application under 35 U.S.C. 371 and claims the benefit ofPCT Application No. PCT/JP2019/024472 having an international filingdate of 20 Jun. 2019, which designated the United States, which PCTapplication claimed the benefit of Japanese Patent Application No.2018-142986, filed 30 Jul. 2018, the entire disclosures of each of whichare incorporated herein by reference.

TECHNICAL FIELD

The present technology relates to a solid-state imaging element and anelectronic device.

BACKGROUND ART

These days, solid-state imaging elements such as charge-coupled device(CCD) image sensors or complementary metal oxide semiconductor (CMOS)image sensors are actively studied in order to achievemicrominiaturization and image quality enhancement of digital camerasand the like.

For example, an imaging element having a stacked layer structure of alower-layer semiconductor layer containing IGZO and an upper-layerphotoelectric conversion layer is proposed (see Patent Document 1).

CITATION LIST Patent Document

-   Patent Document 1: Japanese Patent Application Laid-Open No.    2017-157816

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, the technology proposed by Patent Document 1 has a concern thatfurther improvement in the reliability of the solid-state imagingelement cannot be achieved.

Thus, the present technology has been made in view of such a situation,and a main object of the present technology is to provide a solid-stateimaging element and an electronic device capable of further improvingreliability.

Solutions to Problems

The present inventors conducted extensive studies in order to solve theobject described above, and consequently have, surprisingly, succeededin dramatically improving the reliability of the solid-state imagingelement and have completed the present technology.

In the present technology, as a first aspect, first, there is provided asolid-state imaging element including at least a first photoelectricconversion section, and a semiconductor substrate, in which a secondphotoelectric conversion section is formed, in this order from a lightincidence side, in which

the first photoelectric conversion section includes at least a firstelectrode, a photoelectric conversion layer, a first oxide semiconductorlayer, a second oxide semiconductor layer, and a second electrode inthis order, and

a film density of the first oxide semiconductor layer is higher than afilm density of the second oxide semiconductor layer.

In the solid-state imaging element that is the first aspect of thepresent technology, a hydrogen concentration of the first oxidesemiconductor layer may be lower than a hydrogen concentration of thesecond oxide semiconductor layer.

In the solid-state imaging element that is the first aspect of thepresent technology, the photoelectric conversion layer may contain atleast one organic semiconductor material.

In the solid-state imaging element that is the first aspect of thepresent technology, the first photoelectric conversion section mayfurther include an n-type buffer layer between the photoelectricconversion layer and the first oxide semiconductor layer.

In the solid-state imaging element that is the first aspect of thepresent technology, the first photoelectric conversion section mayfurther include a p-type buffer layer between the first electrode andthe photoelectric conversion layer.

In the solid-state imaging element that is the first aspect of thepresent technology, the first photoelectric conversion section mayfurther include an n-type buffer layer between the photoelectricconversion layer and the first oxide semiconductor layer, and

the first photoelectric conversion section may further include a p-typebuffer layer between the first electrode and the photoelectricconversion layer.

In the present technology, as a second aspect, there is provided asolid-state imaging element including at least: a first photoelectricconversion section, and a semiconductor substrate in which a secondphotoelectric conversion section is formed, in this order from a lightincidence side, in which

the first photoelectric conversion section includes at least a firstelectrode, a photoelectric conversion layer, a first oxide semiconductorlayer, a second oxide semiconductor layer, and a second electrode inthis order, and

a hydrogen concentration of the first oxide semiconductor layer is lowerthan a hydrogen concentration of the second oxide semiconductor layer.

In the solid-state imaging element that is the second aspect of thepresent technology, a film density of the first oxide semiconductorlayer may be higher than a film density of the second oxidesemiconductor layer.

In the solid-state imaging element that is the second aspect of thepresent technology, the photoelectric conversion layer may contain atleast one organic semiconductor material.

In the solid-state imaging element that is the second aspect of thepresent technology, the first photoelectric conversion section mayfurther include an n-type buffer layer between the photoelectricconversion layer and the first oxide semiconductor layer.

In the solid-state imaging element that is the second aspect of thepresent technology, the first photoelectric conversion section mayfurther include a p-type buffer layer between the first electrode andthe photoelectric conversion layer.

In the solid-state imaging element according to the second aspect of thepresent technology, the first photoelectric conversion section mayfurther include an n-type buffer layer between the photoelectricconversion layer and the first oxide semiconductor layer, and

the first photoelectric conversion section may further include a p-typebuffer layer between the first electrode and the photoelectricconversion layer.

In the present technology, as a third aspect, there is provided asolid-state imaging element including at least a first photoelectricconversion section, and a semiconductor substrate in which a secondphotoelectric conversion section is formed, in this order from a lightincidence side, in which

the first photoelectric conversion section includes at least a firstelectrode, a photoelectric conversion layer, a first oxide semiconductorlayer, a second oxide semiconductor layer, and a second electrode inthis order,

a film density of the first oxide semiconductor layer is higher than afilm density of the second oxide semiconductor layer, and a hydrogenconcentration of the first oxide semiconductor layer is lower than ahydrogen concentration of the second oxide semiconductor layer.

In the solid-state imaging element that is the third aspect of thepresent technology, the photoelectric conversion layer may contain atleast one organic semiconductor material.

In the solid-state imaging element that is the third aspect of thepresent technology, the first photoelectric conversion section mayfurther include an n-type buffer layer between the photoelectricconversion layer and the first oxide semiconductor layer.

In the solid-state imaging element that is the third aspect of thepresent technology, the first photoelectric conversion section mayfurther include a p-type buffer layer between the first electrode andthe photoelectric conversion layer.

In the solid-state imaging element according to the third aspect of thepresent technology, the first photoelectric conversion section mayfurther include an n-type buffer layer between the photoelectricconversion layer and the first oxide semiconductor layer, and

the first photoelectric conversion section may further include a p-typebuffer layer between the first electrode and the photoelectricconversion layer.

In the present technology, as a fourth aspect, there is provided anelectronic device including a solid-state imaging element that is anyone aspect among the solid-state imaging elements that are the firstaspect to the third aspect of the present technology.

Effects of the Invention

According to the present technology, the reliability of a solid-stateimaging element can be improved. Note that the effect described hereinis not necessarily a limitative one, and any of the effects described inthe present disclosure is possible.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing a configuration example of asolid-state imaging element to which the present technology is applied.

FIG. 2 is cross-sectional views schematically showing configurationexamples of a first oxide semiconductor layer and a second oxidesemiconductor layer included in a solid-state imaging element to whichthe present technology is applied.

FIG. 3 is a diagram showing relationships between annealing in a watervapor atmosphere and the hydrogen concentration in the first oxidesemiconductor layer.

FIG. 4 is a diagram showing relationships between deuterium after heavywater annealing and the film density of the first oxide semiconductorlayer.

FIG. 5 is a diagram showing relationships between the flow rate ofoxygen gas and the film density of the first oxide semiconductor layer.

FIG. 6 is a diagram for describing TFT characteristics depending ontimes before and after annealing in a water vapor atmosphere.

FIG. 7 is a block diagram showing an overall configuration of asolid-state imaging element to which the present technology is applied.

FIG. 8 is a diagram showing use examples of solid-state imaging elementsto which the present technology is applied.

FIG. 9 is a functional block diagram of an example of an electronicdevice to which the present technology is applied.

FIG. 10 is a view showing an example of a schematic configuration of anendoscopic surgery system.

FIG. 11 is a block diagram showing an example of a functionalconfiguration of a camera head and a camera control unit (CCU).

FIG. 12 is a block diagram showing an example of schematic configurationof a vehicle control system.

FIG. 13 is a diagram of assistance in explaining an example ofinstallation positions of an outside-vehicle information detectingsection and an imaging unit.

MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, preferred forms for implementing the present technology aredescribed. The embodiments described below show only examples of typicalembodiments of the present technology, and the scope of the presenttechnology should not be construed as being limited by them. Note that,unless otherwise specified, in a drawing, “upper” means the upwarddirection or the upper side in the drawing, “lower” means the downwarddirection or the lower side in the drawing, “left” means the leftdirection or the left side in the drawing, and “right” means the rightdirection or the right side in the drawing. Further, in the drawings,identical or equivalent elements or members are marked with the samereference sign, and a repeated description is omitted.

Note that the description is given in the following order.

1. Outline of present technology

2. First embodiment (example 1 of solid-state imaging element)

3. Second embodiment (example 2 of solid-state imaging element)

4. Third embodiment (example 3 of solid-state imaging element)

5. Fourth embodiment (example of electronic device)

6. Use examples of solid-state imaging elements to which presenttechnology is applied

7. Application example to endoscopic surgery system

8. Application example to mobile bodies

1. Outline of Present Technology

First, an outline of the present technology is described.

To obtain high-grade TFT characteristics and high reliability with, forexample, an IGZO film, hydrogen termination by annealing in a watervapor atmosphere after film formation is necessary. This is because areduction in trap density can be achieved by hydrogen termination.Meanwhile, a single IGZO film with a high film density has a lowhydrogen diffusion rate. Thus, a film with a low film density that iseasily hydrogen-terminated is preferable to create a high-grade state upto a channel section of a bottom portion of the film.

On the other hand, if an IGZO film with a low film density is employed,the vicinity of a surface (for example, the interface between the IGZOfilm and a photoelectric conversion layer (an n-type buffer layer), thesame applies hereinafter) is likely to experience OH adsorption andwater (H₂O) elimination, and undergoes carrier formation.

An oxide semiconductor, for example, is used for a charge accumulationlayer (an oxide semiconductor layer); however, the surface of the chargeaccumulation layer (the oxide semiconductor layer) is unstable, andtherefore there is a case where oxygen deficiency is likely to occur atthe interface between a photoelectric conversion layer (a photoelectricconversion film) and the charge accumulation layer (the oxidesemiconductor layer).

From the above, a second oxide semiconductor layer of a lower layer isset to be a low film density layer with good hydrogen diffusibility, anda first oxide semiconductor layer of an upper layer is set to be a highfilm density layer that suppresses OH adsorption and the elimination ofwater (H₂O); thereby, carrier generation in the vicinity of a surface(for example, the interface between the IGZO film and a photoelectricconversion layer (an n-type buffer layer)) can be suppressed. Further,hydrogen elimination in the vicinity of the surface can be suppressed bysetting the first oxide semiconductor layer to have a lower hydrogenconcentration than the second oxide semiconductor layer.

That is, a solid-state imaging element according to the presenttechnology is a solid-state imaging element in which a first oxidesemiconductor layer included in the solid-state imaging elementaccording to the present technology has a higher film density, has alower hydrogen concentration, or has a higher film density and has alower hydrogen concentration than a second oxide semiconductor layerincluded in the solid-state imaging element according to the presenttechnology in order to suppress OH adsorption and H₂O elimination ofsurfaces of the first and second oxide semiconductor layers, for examplesurfaces of IGZO.

Hereinbelow, a solid-state imaging element of an embodiment according tothe present technology is described in detail.

2. First Embodiment (Example 1 of Solid-State Imaging Element)

A solid-state imaging element of a first embodiment according to thepresent technology (example 1 of the solid-state imaging element) is asolid-state imaging element that includes at least a first photoelectricconversion section and a semiconductor substrate in which a secondphotoelectric conversion section is formed, in this order from the lightincidence side, in which the first photoelectric conversion sectionincludes at least a first electrode, a photoelectric conversion layer, afirst oxide semiconductor layer, a second oxide semiconductor layer, anda second electrode in this order and the film density of the first oxidesemiconductor layer is higher than the film density of the second oxidesemiconductor layer.

The reliability of a solid-state imaging element can be improved by thesolid-state imaging element of the first embodiment according to thepresent technology. In more detail, by the introduction of the firstoxide semiconductor layer, which is a high density layer, theelimination of water (H₂O) sent from an oxide semiconductor of thesecond oxide semiconductor layer is suppressed, and an increase incarrier concentration of a surface of the first oxide semiconductorlayer in contact with the photoelectric conversion layer (or an n-typebuffer layer described later) can be suppressed.

The value of the film density of the first oxide semiconductor layer maybe any value, but is preferably 6.11 to 6.35 g/cm³, and the value of thefilm density of the second oxide semiconductor layer may be any value,but is preferably 5.80 to 6.10 g/cm³.

In the solid-state imaging element of the first embodiment according tothe present technology, the hydrogen concentration of the first oxidesemiconductor layer is preferably lower than the hydrogen concentrationof the second oxide semiconductor layer. The hydrogen concentration ofthe first oxide semiconductor layer may be any concentration, but ispreferably 1.0E18 to 9.0E19 atoms/cm², and the hydrogen concentration ofthe second oxide semiconductor layer may be any concentration, but ispreferably 1.0E20 to 5.0E21 atoms/cm².

FIG. 1 shows a solid-state imaging element 10 that is an example of thesolid-state imaging element of the first embodiment according to thepresent technology. FIG. 1 is a cross-sectional view of the solid-stateimaging element 10. The solid-state imaging element 10 is included in,for example, one pixel (a unit pixel P) in an imaging device such as aCMOS image sensor (an imaging device 1001, see FIG. 8 ).

The solid-state imaging element 10 includes a semiconductor substrate 30in which a second photoelectric conversion section (not illustrated) isformed and a first photoelectric conversion section 10A. The solid-stateimaging element 10 includes a photoelectric conversion layer 15 betweena lower electrode 11 (a second electrode) and an upper electrode (afirst electrode) 16 that are arranged facing each other. A first oxidesemiconductor layer 14 and a second oxide semiconductor layer 13 areprovided between the lower electrode (second electrode) 11 and thephotoelectric conversion layer 15 via an insulating layer 12, in thisorder from the side of the photoelectric conversion layer 15 (the upperside of FIG. 1 ). The lower electrode 11 includes, as a plurality ofmutually independent electrodes, a readout electrode 11A, anaccumulation electrode 11B, and a transfer electrode 11C that is placedbetween, for example, the readout electrode 11A and the accumulationelectrode 11B, the accumulation electrode 11B and the transfer electrode11C are covered by the insulating layer 12, and the readout electrode11A is electrically connected to the second oxide semiconductor layer 13via an opening W provided in the insulating layer 12.

Note that, in the solid-state imaging element 10, an n-type buffer layer18 is provided between the first oxide semiconductor layer 14 and thephotoelectric conversion layer 15, and a p-type buffer layer 17 isprovided between the upper electrode (first electrode) 16 and thephotoelectric conversion layer 15. Further, in the solid-state imagingelement 10, a sealing film 19 is formed so as to cover the firstphotoelectric conversion section 10A.

Each of the first oxide semiconductor layer 14 and the second oxidesemiconductor layer 13 contains an oxide semiconductor material.Examples of the oxide semiconductor material include IGZO (anIn—Ga—Zn—O-based oxide semiconductor), ZTO (a Zn—Sn—O-based oxidesemiconductor), IGZTO (an In—Ga—Zn—Sn—O-based oxide semiconductor), GTO(a Ga—Sn—O-based oxide semiconductor), and IGO (an In—Ga—O-based oxidesemiconductor). Each of the first oxide semiconductor layer 14 and thesecond oxide semiconductor layer 13 preferably uses at least one of theoxide semiconductor materials mentioned above, and preferably uses,among them, IGZO.

The total thickness of the first oxide semiconductor layer 14 and thesecond oxide semiconductor layer 13 is, for example, not less than 30 nmand not more than 200 nm, and preferably not less than 50 nm and notmore than 150 nm.

Each of the first oxide semiconductor layer 14 and the second oxidesemiconductor layer 13 is a layer for accumulating a signal chargegenerated in the photoelectric conversion layer 15 and transferring thesignal charge to the readout electrode 11A. Each of the first oxidesemiconductor layer 14 and the second oxide semiconductor layer 13preferably uses a material that has a higher mobility of charge than thephotoelectric conversion layer 15 and yet has a large band gap. Thereby,for example, the speed of charge transfer can be improved, and theinjection of holes from the readout electrode 11A to the first oxidesemiconductor layer 14 and the second oxide semiconductor layer 13 issuppressed.

The photoelectric conversion layer 15 is a layer that converts lightenergy to electrical energy, and is, for example, a layer that providesa field where an exciton generated when the layer absorbs light in thewavelength range of not less than 400 nm and not more than 2500 nmseparates into an electron and a hole. The thickness of thephotoelectric conversion layer 15 is, for example, not less than 100 nmand not more than 1000 nm, and preferably not less than 300 nm and notmore than 800 nm.

Examples of materials to be contained in the photoelectric conversionlayer 15 include organic-based materials and inorganic-based materials.

In a case where the photoelectric conversion layer 15 contains anorganic-based material, the photoelectric conversion layer may haveconfigurations like below ((1) to (4)).

Any of the following four types may be employed.

(1) Containing a p-type organic semiconductor.

(2) Containing an n-type organic semiconductor.

(3) Including a stacked structure of a p-type organic semiconductorlayer and an n-type organic semiconductor layer. Including a stackedstructure of a p-type organic semiconductor layer, a mixed layer (a bulkheterostructure) of a p-type organic semiconductor and an n-type organicsemiconductor, and an n-type organic semiconductor layer. Including astacked structure of a p-type organic semiconductor layer and a mixedlayer (a bulk heterostructure) of a p-type organic semiconductor and ann-type organic semiconductor. Including a stacked structure of an n-typeorganic semiconductor layer and a mixed layer (a bulk heterostructure)of a p-type organic semiconductor and an n-type organic semiconductor.

(4) Including a mixture (a bulk heterostructure) of a p-type organicsemiconductor and an n-type organic semiconductor.

(4) Including a mixture (a bulk heterostructure) of a p-type organicsemiconductor and an n-type organic semiconductor. However, the stackingorder may be arbitrarily changed.

As the p-type organic semiconductor, naphthalene derivatives, anthracenederivatives, phenanthrene derivatives, pyrene derivatives, perylenederivatives, tetracene derivatives, pentacene derivatives, quinacridonederivatives, thiophene derivatives, thienothiophene derivatives,benzothiophene derivatives, benzothienobenzothiophene derivatives,triallylamine derivatives, carbazole derivatives, perylene derivatives,picene derivatives, chrysene derivatives, fluoranthene derivatives,phthalocyanine derivatives, subphthalocyanine derivatives,subporphyrazine derivatives, a metal complex having a heterocycliccompound as a ligand, polythiophene derivatives, polybenzothiadiazolederivatives, polyfluorene derivatives, and the like may be given.

As the n-type organic semiconductor, fullerenes and fullerenederivatives (for example, fullerenes such as C60, C70, and C74 (higherfullerenes), endohedral fullerenes and the like, and fullerenederivatives (for example, fullerene fluorides, PCBM fullerene compounds,fullerene polymers, and the like)), an organic semiconductor having alarger (deeper) HOMO and a larger (deeper) LUMO than the p-type organicsemiconductor, and transparent inorganic metal oxides may be given. Asthe n-type organic semiconductor, specifically, an organic molecule, anorganic metal complex, or a subphthalocyanine derivative having, in partof the molecular framework, a heterocyclic compound containing anitrogen atom, an oxygen atom, or a sulfur atom, such as a pyridinederivative, a pyrazine derivative, a pyrimidine derivative, a triazinederivative, a quinoline derivative, a quinoxaline derivative, anisoquinoline derivative, an acridine derivative, a phenazine derivative,a phenanthroline derivative, a tetrazole derivative, a pyrazolederivative, an imidazole derivative, a thiazole derivative, an oxazolederivative, an imidazole derivative, a benzimidazole derivative, abenzotriazole derivative, a benzoxazole derivative, a benzoxazolederivative, a carbazole derivative, a benzofuran derivative, adibenzofuran derivative, a subporphyrazine derivative, a polyphenylenevinylene derivative, a polybenzothiadiazole derivative, or apolyfluorene derivative, may be given. Examples of groups or the likeincluded in the fullerene derivative include a halogen atom; astraight-chain, branched, or cyclic alkyl group or a phenyl group; agroup having a straight-chain or annelated aromatic compound; a grouphaving a halide; a partial fluoroalkyl group; a perfluoroalkyl group; asilylalkyl group; a silylalkoxy group; an arylsilyl group; anarylsulfanyl group; an alkylsulfanyl group; an arylsulfonyl group; analkylsulfonyl group; an aryl sulfide group; an alkyl sulfide group; anamino group; an alkylamino group; an arylamino group; a hydroxy group;an alkoxy group; an acylamino group; an acyloxy group; a carbonyl group;a carboxy group; a carboxamide group; a carboalkoxy group; an acylgroup; a sulfonyl group; a cyano group; a nitro group; a group having achalcogenide; a phosphine group; and a phosphono group; and derivativesof these. The thickness of the photoelectric conversion layer containingan organic-based material (occasionally called as an “organicphotoelectric conversion layer”) is not limited, but is, for example,1×10⁻⁸ m to 5×10⁻⁷ m, preferably 2.5×10⁻⁸ m to 3×10⁻⁷ m, more preferably2.5×10⁻⁸ m to 2×10⁻⁷ m, and still more preferably 1×10⁻⁷ m to 1.8×10⁻⁷m.

Note that, although organic semiconductors are often classified into thep-type and the n-type, the p-type means that it is easy to transportholes and the n-type means that it is easy to transport electrons, andthe p-type and the n-type are not limited to the interpretation ofhaving holes or electrons as the majority carrier of thermal excitationlike in inorganic semiconductors.

Alternatively, as materials to be contained in an organic photoelectricconversion layer that photoelectrically converts light of the wavelengthof green, for example, rhodamine-based dyes, merocyanine-based dyes,quinacridone derivatives, subphthalocyanine-based dyes(subphthalocyanine derivatives), and the like may be given; as materialsto be contained in an organic photoelectric conversion layer thatphotoelectrically converts blue light, for example, coumarinic aciddyes, tris(8-hydroxyquinolinato)aluminum (Alq3), merocyanine-based dyes,and the like may be given; and as materials to be contained in anorganic photoelectric conversion layer that photoelectrically convertsred light, for example, phthalocyanine-based dyes andsubphthalocyanine-based dyes (subphthalocyanine derivatives) may begiven.

Alternatively, as inorganic-based materials to be contained in thephotoelectric conversion layer, crystalline silicon, amorphous silicon,microcrystalline silicon, crystalline selenium, amorphous selenium,CuInGaSe (GIGS), CuInSe₂ (CIS), CuInS₂, CuAlS₂, CuAlSe₂, CuGaS₂,CuGaSe₂, AgAlS₂, AgAlSe₂, AgInS₂, and AgInSe₂, which arechalcopyrite-based compounds, GaAs, InP, AlGaAs, InGaP, AlGaInP, andInGaAsP, which are group III-V compounds, and compound semiconductorssuch as CdSe, CdS, In₂Se₃, In₂S₃, Bi₂Se₃, Bi₂S₃, ZnSe, ZnS, PbSe, andPbS may be given. In addition, quantum dots containing these materialsmay be used for the photoelectric conversion layer.

The second electrode 11 (11A to 11C) is preferably a transparentelectrode containing a transparent electrically conductive material. Thesecond electrodes 11A to 11C may contain the same material, or maycontain different materials. Each of the second electrodes 11A to 11Ccan be formed by the sputtering method or the chemical vapor depositionmethod (CVD).

Examples of the transparent electrically conductive material includeindium oxide, an indium-tin oxide (ITO, indium tin oxide, includingSn-doped In₂O₃, crystalline ITO, and amorphous ITO), an indium-zincoxide (IZO, indium zinc oxide) in which indium is added as a dopant tozinc oxide, an indium-gallium oxide (IGO) in which indium is added as adopant to gallium oxide, an indium-gallium-zinc oxide (IGZO, In—GaZnO₄)in which indium and gallium are added as dopants to zinc oxide, anindium-tin-zinc oxide (ITZO) in which indium and tin are added asdopants to zinc oxide, IFO (F-doped In₂O₃), tin oxide (SnO₂), ATO(Sb-doped SnO₂), FTO (F-doped SnO₂), zinc oxide (including ZnO dopedwith other elements), an aluminum-zinc oxide (AZO) in which aluminum isadded as a dopant to zinc oxide, a gallium-zinc oxide (GZO) in whichgallium is added as a dopant to zinc oxide, titanium oxide (TiO₂), aniobium-titanium oxide (TNO) in which niobium is added as a dopant totitanium oxide, antimony oxide, a spinel-type oxide, and an oxide havinga YbFe₂O₄ structure.

The first electrode 16 includes, for example, a transparent electricallyconductive film such as an indium tin oxide film or an indium zinc oxidefilm, or the like.

As the material of the insulating layer 12, inorganic-based insulatingmaterials such as silicon oxide-based materials, silicon nitride(SiN_(x)), and metal oxide high-dielectric insulating materials such asaluminum oxide (Al₂O₃) are given. In addition, organic-based insulatingmaterials (organic polymers), examples including polymethyl methacrylate(PMMA), polyvinylphenol (PVP), polyvinyl alcohol (PVA), polyimides,polycarbonates (PC), polyethylene terephthalate (PET), polystyrene,silanol derivatives (silane coupling agents) such asN-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS),3-mercaptopropyltrimethoxysilane (MPTMS), and octadecyltrichlorosilane(OTS), novolak-type phenolic resins, fluorine-based resins, and astraight-chain hydrocarbon having, at one end, a functional groupcapable of binding to a control electrode, such as octadecanethiol anddodecyl isocyanate, may be given, and these may be used in combination.Note that, as silicon oxide-based materials, silicon oxide (SiO_(x)),BPSG, PSG, BSG, AsSG, PbSG, silicon oxynitride (SiON), SOG (spin-onglass), and low-permittivity materials (for example, polyaryl ethers,cycloperfluorocarbon polymers, benzocyclobutene, cyclic fluororesins,polytetrafluoroethylene, fluorinated aryl ethers, fluorinatedpolyimides, amorphous carbon, and organic SOG) are given.

The insulating layer 12 is a layer for electrically separating theaccumulation electrode 11B and the transfer electrode 11C, and thesecond oxide semiconductor layer 13. The insulating layer 12 is providedso as to cover the lower electrode 11. Further, in the insulating layer12, an opening is provided on the readout electrode 11A of the lowerelectrode 11, and the readout electrode 11A and the charge accumulationlayer 13 are electrically connected via the opening. The side surface ofthe opening 12H preferably has, for example, an inclination expandingtoward the light incidence side S1, as shown in FIG. 2 . Thereby, themovement of charge from the charge accumulation layer 13 to the readoutelectrode (third electrode) 11A is smoothed.

The p-type buffer layer 17 is a layer for promoting the supply of holesgenerated by the photoelectric conversion layer 15 to the firstelectrode 16, and may contain, for example, molybdenum oxide (MoO₃),nickel oxide (NiO), vanadium oxide (V₂O₅), or the like. The p-typebuffer layer (hole transportation layer) may contain an organic materialsuch as poly(3,4-ethylenedioxythiophene) (PEDOT),N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), or4,4′,4″-tris[2-naphthyl(phenyl)amino]triphenylamine (2T-NATA).

The n-type buffer layer 18 is a layer for promoting the supply ofelectrons generated by the photoelectric conversion layer 15 to thesecond electrode 11A, and may contain, for example, titanium oxide(TiO₂), zinc oxide (ZnO), or the like. The n-type buffer layer 18 may beformed also by stacking titanium oxide and zinc oxide. Further, then-type buffer layer 18 may contain a high-molecular semiconductormaterial or an organic-based material such as a material that is anorganic molecule or an organic metal complex including a heterocycleincluding N as part of the molecular framework, such as pyridine,quinoline, acridine, indole, imidazole, benzimidazole, orphenanthroline, and that has limited absorption in the visible lightregion.

The readout electrode 11A is an electrode for transferring a signalcharge generated in the photoelectric conversion layer 15 to a floatingdiffusion section (not illustrated).

The accumulation electrode 11B is an electrode for accumulating, in thefirst oxide semiconductor layer 14 and the second oxide semiconductorlayer 13, a signal charge (electrons) out of the charges generated inthe photoelectric conversion layer 15. The accumulation electrode 11B ispreferably larger than the readout electrode 11A, and can therebyaccumulate a large amount of charge.

The transfer electrode 11C is an electrode for improving the efficiencyof transfer of charge accumulated in the accumulation electrode 11B tothe readout electrode 11A, and is provided between the readout electrode11A and the accumulation electrode 11B. The transfer electrode 11C is,for example, connected to a pixel driving circuit included in a drivingcircuit. The readout electrode 11A, the accumulation electrode 11B, andthe transfer electrode 11C can apply voltage independently of eachother.

The solid-state imaging element of the first embodiment according to thepresent technology can be manufactured by using a known method, forexample, the sputtering method, a method of performing patterning byphotolithography technology and performing dry etching or wet etching,or a wet film formation method. Examples of the wet film formationmethod include the spin coating method, the immersion method, thecasting method, various printing methods such as the screen printingmethod, the inkjet printing method, the offset printing method, and thegravure printing method, the stamping method, the spraying method, andvarious coating methods such as the air doctor coater method, the bladecoater method, the rod coater method, the knife coater method, thesqueeze coater method, the reverse roll coater method, the transfer rollcoater method, the gravure coater method, the kiss coater method, thecast coater method, the spray coater method, the slit orifice coatermethod, and the calender coater method.

FIG. 7 is a functional block diagram showing a solid-state imagingelement 1001. The solid-state imaging element 1001 is a CMOS imagesensor and has a pixel section 101 a as an imaging area, and has, forexample, a circuit section 130 including a row scanning section 131, ahorizontal selection section 133, a column scanning section 134, and asystem control section 132. Provided in a region around the pixelsection 101 a or stacked with the pixel section 101 a, the circuitsection 130 may be provided in a region around the pixel section 101 a,or may be provided to be stacked with the pixel section 101 a (in aregion facing the pixel section 101 a).

The pixel section 101 a has, for example, a plurality of unit pixels P(each of which corresponds to, for example, the solid-state imagingelement 10 (serving as one pixel)) that are two-dimensionally arrangedin a matrix form. In the unit pixel P, for example, a pixel driving lineLread (specifically, a row selection line and a reset control line) isdrawn for each pixel row, and a vertical signal line Lsig is drawn foreach pixel column. The pixel driving line Lread is a line that transmitsa driving signal for reading out a signal sent from the pixel. One endof the pixel driving line Lread is connected to an output endcorresponding to a row of the row scanning section 131.

The row scanning section 131 is a pixel driving unit that includes ashift register, an address decoder, etc. and that drives each pixel P ofthe pixel section 101 a, for example on a row basis. Signals outputtedfrom the pixels P of the pixel rows selectively scanned by the rowscanning section 131 are supplied to the horizontal selection section133 through the respective vertical signal lines Lsig. The horizontalselection section 133 includes amplifiers, horizontal selectionswitches, etc. provided individually for the vertical signal lines Lsig.

The column scanning section 134 is a section that includes a shiftregister, an address decoder, etc. and that sequentially scans anddrives the horizontal selection switches of the horizontal selectionsection 133. By the selective scanning by the column scanning section134, signals of the pixels transmitted through the vertical signal linesLsig are sequentially transmitted to a horizontal signal line 135, andare outputted to the outside through the horizontal signal line 135.

The system control section 132 is a section that receives clocks givenfrom the outside, data for issuing commands of operating modes, etc. andfurther outputs data of inside information of the solid-state imagingelement 1001, etc. The system control section 132 further includes atiming generator that generates various timing signals, and performs thedriving control of the row scanning section 131, the horizontalselection section 133, the column scanning section 134, etc., on thebasis of various timing signals generated by the timing generator.

FIG. 2 is cross-sectional views schematically showing configurationexamples of a first oxide semiconductor layer and a second oxidesemiconductor layer included in a solid-state imaging element accordingto the present technology. FIG. 2(a) shows a second oxide semiconductorlayer 13 a, FIG. 2(b) shows that a first oxide semiconductor layer 14 bwith a low hydrogen concentration is provided on a second oxidesemiconductor layer 13 b (which can be used for, for example, asolid-state imaging element of a second embodiment described later), andFIG. 2(c) shows that a first oxide semiconductor layer 14 c with a highfilm density is provided on a second oxide semiconductor layer 13 c(which can be used for, for example, the solid-state imaging element ofthe first embodiment). Each of the second oxide semiconductor layers 13a, 13 b, and 13 c is a film having few traps, and is in a state of beinghydrogen-terminated by H₂O annealing or the like; thus, each of thesecond oxide semiconductor layers 13 a, 13 b, and 13 c is a film inwhich some amount of hydrogen is contained, and has such a film densityas to be recovered by annealing. The first oxide semiconductor layer 14b is a film that suppresses the hydrogen elimination of the surface, andthe first oxide semiconductor layer 14 c is a dehydration suppressionfilm.

FIG. 3 is a diagram showing relationships between annealing in a watervapor atmosphere and the hydrogen concentration in the first oxidesemiconductor layer. The horizontal axis of FIG. 3 represents the depth(the length in the thickness direction) (Depth (nm)) of the first oxidesemiconductor layer (or the second oxide semiconductor layer), the leftside of the vertical axis of FIG. 3 represents the H/O concentration(atoms/cm³), and the right side of the vertical axis of FIG. 3represents the counts. Data of hydrogen (H) and oxygen (O) correspond tothe left side (the H/O concentration (atoms/cm³)) of the vertical axisof FIG. 3 , and data of indium (In) and gallium (Ga) correspond to theright side (the counts) of the vertical axis of FIG. 3 . The filmthickness (depth) of the first oxide semiconductor layer (or the secondoxide semiconductor layer) can be found by using data of indium (In),gallium (Ga), and oxygen (O).

FIG. 3(a) is a diagram showing a relationship with the hydrogenconcentration in the first oxide semiconductor layer when annealing isnot performed, FIG. 3(b) is a diagram showing a relationship betweenannealing (150° C., 2 hours) and the hydrogen concentration in the firstoxide semiconductor layer, and FIG. 3(c) is a diagram showing arelationship between annealing (350° C., 2 hours) and the hydrogenconcentration in the first oxide semiconductor layer. FIG. 3 shows anincrease in hydrogen concentration in the first oxide semiconductorlayer (in the film) depending on the annealing temperature in a watervapor atmosphere. With annealing of 150° C. (×2 hours), there is nochange from immediately after film formation (annealing is notperformed); however, at 350° C. (×2 hours), hydrogen concentrations ofnot less than the 20th power are obtained with a gradient from thesurface side of the film to a depth of 100 nm. Note that FIG. 3similarly applies to the second oxide semiconductor layer.

FIG. 4 is a diagram showing relationships between deuterium after heavywater annealing and the film density of the first oxide semiconductorlayer. The horizontal axis of FIG. 4 represents the depth (the length inthe thickness direction) (Depth (nm)) of the first oxide semiconductorlayer (or the second oxide semiconductor layer), the left side of thevertical axis of FIG. 4 represents the D/H/O concentration (atoms/cm³),and the right side of the vertical axis of FIG. 4 represents the counts.Data of deuterium (D), hydrogen (H), and oxygen (O) correspond to theleft side (the D/H/O concentration (atoms/cm³)) of the vertical axis ofFIG. 4 , and data of indium (In) and gallium (Ga) correspond to theright side (the counts) of the vertical axis of FIG. 4 . The filmthickness (depth) of the first oxide semiconductor layer (or the secondoxide semiconductor layer) can be found by using data of indium (In),gallium (Ga), and oxygen (O).

FIG. 4(a) is a diagram showing relationships between deuterium afterheavy water annealing and the film density of the first oxidesemiconductor layer (6.12 g/cm³), and FIG. 4(b) is a diagram showingrelationships between deuterium after heavy water annealing and the filmdensity of the first oxide semiconductor layer (6.28 g/cm3). FIG. 4shows a difference in hydrogen concentration in annealing in a watervapor atmosphere depending on the film density of the first oxidesemiconductor layer (an IGZO film). In order to make a distinction withhydrogen originally existing in the film, annealing was performed in adeuterium water atmosphere. At a film density of 6.12 g/cm³ (FIG. 4(a)),values not less than 1E20 atoms/cm³ are obtained; however, at a filmdensity of 6.28 g/cm³ (FIG. 4(b)), the hydrogen concentration is notmore than 1E20 atoms/cm³. Note that FIG. 4 similarly applies to thesecond oxide semiconductor layer.

FIG. 5 is a diagram showing relationships between the flow rate ofoxygen gas and the film density of the first oxide semiconductor layer.The horizontal axis of FIG. 5 represents the O²/(Ar+O²) flow ratio, andthe vertical axis of FIG. 5 represents the XRD density [/cm³].

If the flow rate of oxygen gas is increased or decreased, the filmdensity can be changed. The film density can be changed also by changingthe input power (Power A and Power B shown in FIG. 5 ). Note that FIG. 5similarly applies to the second oxide semiconductor layer.

FIG. 6 is a diagram for describing TFT characteristics depending ontimes before and after annealing in a water vapor atmosphere. Thehorizontal axis of FIG. 6 represents V_(GS) [V] (the gate voltage), andthe vertical axis of FIG. 6 represents I_(D) [A] (the drain current).

Id-Vg characteristics of a TFT using an IGZO film (the first oxidesemiconductor layer) before and after annealing in a water vaporatmosphere will now be shown. As shown in FIG. 6 , by a reduction in thenumber of in-film traps by hydrogen introduction, the threshold voltageis made near 0 V, and a steep rise is exhibited. Note that FIG. 6similarly applies to the second oxide semiconductor layer.

3. Second Embodiment (Example 2 of Solid-State Imaging Element)

A solid-state imaging element of a second embodiment according to thepresent technology (example 2 of the solid-state imaging element) is asolid-state imaging element that includes at least a first photoelectricconversion section and a semiconductor substrate in which a secondphotoelectric conversion section is formed, in this order from the lightincidence side, in which the first photoelectric conversion sectionincludes at least a first electrode, a photoelectric conversion layer, afirst oxide semiconductor layer, a second oxide semiconductor layer, anda second electrode in this order and the hydrogen concentration of thefirst oxide semiconductor layer is lower than the hydrogen concentrationof the second oxide semiconductor layer.

The reliability of a solid-state imaging element can be improved by thesolid-state imaging element of the second embodiment according to thepresent technology. In more detail, an increase in carrier concentrationdue to H₂O elimination toward the side of the photoelectric conversionlayer (an n-type buffer layer) is suppressed by the introduction of thefirst oxide semiconductor layer, which is a low hydrogen concentrationlayer. That is, in the first oxide semiconductor layer having a lowhydrogen concentration, water (H₂O) is less likely to be eliminated, andthe occurrence of oxygen deficiency of a surface (a surface in contactwith the photoelectric conversion layer (or the n-type buffer layer))can be suppressed.

In the solid-state imaging element of the second embodiment according tothe present technology, the film density of the first oxidesemiconductor layer is preferably higher than the film density of thesecond oxide semiconductor layer.

For the solid-state imaging element of the second embodiment accordingto the present technology, the matter described in the section of thesolid-state imaging element of the first embodiment according to thepresent technology (including the matter regarding FIG. 1 to FIG. 7 )can be applied as it is except for the above description.

4. Third Embodiment (Example 3 of Solid-State Imaging Element)

A solid-state imaging element of a third embodiment according to thepresent technology (example 3 of the solid-state imaging element) is asolid-state imaging element that includes at least a first photoelectricconversion section and a semiconductor substrate in which a secondphotoelectric conversion section is formed, in this order from the lightincidence side, in which the first photoelectric conversion sectionincludes at least a first electrode, a photoelectric conversion layer, afirst oxide semiconductor layer, a second oxide semiconductor layer, anda second electrode in this order, the film density of the first oxidesemiconductor layer is higher than the film density of the second oxidesemiconductor layer, and the hydrogen concentration of the first oxidesemiconductor layer is lower than the hydrogen concentration of thesecond oxide semiconductor layer.

In the solid-state imaging element of the third embodiment according tothe present technology, by the introduction of the first oxidesemiconductor layer, which is a high density layer and has a lowhydrogen concentration, the elimination of H₂O from an oxidesemiconductor of the second oxide semiconductor layer is suppressed, anincrease in carrier concentration of a surface of the first oxidesemiconductor layer in contact with the photoelectric conversion layer(or an n-buffer layer) can be suppressed, and furthermore an increase incarrier concentration due to H₂O elimination toward the side of thephotoelectric conversion layer (the n-type buffer layer) is suppressed.That is, the first oxide semiconductor layer of the solid-state imagingelement of the third embodiment according to the present technology isalso a low hydrogen concentration layer; therefore, water (H₂O) is lesslikely to be eliminated, and the occurrence of oxygen deficiency of asurface (a surface in contact with the photoelectric conversion layer(or the n-buffer layer)) can be suppressed.

For the solid-state imaging element of the third embodiment according tothe present technology, the matter described in the section of thesolid-state imaging element of the first embodiment according to thepresent technology (including the matter regarding FIG. 1 to FIG. 7 )can be applied as it is except for the above description.

5. Fourth Embodiment (Example of Electronic Device)

An electronic device of a fourth embodiment according to the presenttechnology is an electronic device that includes any one solid-stateimaging element of the solid-state imaging elements of the first tothird embodiments according to the present technology. The solid-stateimaging element of the first to third embodiments according to thepresent technology is as mentioned above, and therefore herein adescription is omitted. The electronic device of the fourth embodimentaccording to the present technology includes a solid-state imagingelement having excellent reliability, and can therefore improve thereliability of electronic devices, etc.

6. Use Examples of Solid-State Imaging Elements to which PresentTechnology is Applied

FIG. 8 is a diagram showing use examples of the solid-state imagingelement of the first to third embodiments according to the presenttechnology, as an image sensor.

The solid-state imaging element of the first to third embodimentsdescribed above can be used for, for example, various cases where lightsuch as visible light, infrared light, ultraviolet light, or X-rays issensed, as shown below. That is, as shown in FIG. 8 , the solid-stateimaging element of the first to third embodiments can be used for anapparatus (for example, the electronic device of the fourth embodimentdescribed above) used in the field of appreciation in which images usedfor appreciation are imaged, the field of transportation, the field ofhome electrical appliances, the field of medical service and healthcare, the field of security, the field of beauty culture, the field ofsports, the field of agriculture, etc., for example.

Specifically, in the field of appreciation, for example, the solid-stateimaging element of the first to third embodiments can be used for anapparatus for imaging images used for appreciation, such as a digitalcamera, a smartphone, or a mobile phone provided with a camera function.

In the field of transportation, for example, the solid-state imagingelement of the first to third embodiments can be used for an apparatusused for transportation for safe driving such as automatic stopping, therecognition of the state of a driver, etc., such as a car-mounted sensorthat images the front side, the rear side, the surroundings, the inside,etc. of an automobile, a surveillance camera that monitors movingvehicles and a road, or a distance measuring sensor that performsdistance measuring of the distance between vehicles or the like.

In the field of home electrical appliances, for example, the solid-stateimaging element of the first to third embodiments can be used for anapparatus used for home electrical appliances in order to image agesture of a user and perform device operation in accordance with thegesture, such as a television, a refrigerator, or an air conditioner.

In the field of medical service and health care, for example, thesolid-state imaging element of the first to third embodiments can beused for an apparatus used for medical service and health care, such asan endoscope or an apparatus that performs blood vessel imaging byreceiving infrared light.

In the field of security, for example, the solid-state imaging elementof the first to third embodiments can be used for an apparatus used forsecurity, such as a surveillance camera for crime prevention use or acamera for person authentication use.

In the field of beauty culture, for example, the solid-state imagingelement of the first to third embodiments can be used for an apparatusused for beauty culture, such as a skin measuring device that images askin or a microscope that images the scalp.

In the field of sports, for example, the solid-state imaging element ofthe first to third embodiments can be used for an apparatus used forsports, such as an action camera or a wearable camera for sports use orthe like.

In the field of agriculture, for example, the solid-state imagingelement of the first to third embodiments can be used for an apparatusused for agriculture, such as a camera for monitoring the state of afarm and crops.

Next, use examples of the solid-state imaging element of the first tothird embodiments according to the present technology are specificallydescribed. For example, the solid-state imaging element 1001 describedabove can be used for all types of electronic apparatuses including animaging function, such as camera systems such as digital still camerasand video cameras, and mobile phones having an imaging function. FIG. 9shows, as an example, a rough configuration of an electronic apparatus1002 (a camera). The electronic apparatus 1002 is, for example, a videocamera capable of capturing still images or moving images, and includesa solid-state imaging element 399, an optical system (optical lens) 310,a shutter device 311, a driving unit 313 that drives the solid-stateimaging element 399 and the shutter device 311, and a signal processingsection 312.

The optical system 310 is a system that guides image light (incidencelight) sent from a subject to a pixel section of the solid-state imagingelement 399. The optical system 310 may include a plurality of opticallenses. The shutter device 311 is a device that controls the period oflight irradiation and the period of light blocking for the solid-stateimaging element 399. The driving unit 313 is a section that controls atransfer operation of the solid-state imaging element 399 and a shutteroperation of the shutter device 311. The signal processing section 312is a section that performs various pieces of signal processing on asignal outputted from the solid-state imaging element 399. A video imagesignal Dout after signal processing is stored in a storage medium suchas a memory, or is outputted to a monitor or the like.

7. Application Example to Endoscopic Surgery System

The present technology can be applied to various products. For example,the technology according to the present disclosure (present technology)can be applied to the endoscopic surgery system.

FIG. 10 is a view showing an example of a schematic configuration of anendoscopic surgery system to which the technology according to anembodiment of the present disclosure (present technology) can beapplied.

In FIG. 10 , a state is illustrated in which a surgeon (medical doctor)11131 is using an endoscopic surgery system 11000 to perform surgery fora patient 11132 on a patient bed 11133. As illustrated, the endoscopicsurgery system 11000 includes an endoscope 11100, other surgical tools11110 such as a pneumoperitoneum tube 11111 and an energy device 11112,a supporting arm apparatus 11120 which supports the endoscope 11100thereon, and a cart 11200 on which various apparatus for endoscopicsurgery are mounted.

The endoscope 11100 includes a lens barrel 11101 having a region of apredetermined length from a distal end thereof to be inserted into abody cavity of the patient 11132, and a camera head 11102 connected to aproximal end of the lens barrel 11101. In the example illustrated, theendoscope 11100 is illustrated which includes as a rigid endoscopehaving the lens barrel 11101 of the hard type. However, the endoscope11100 may otherwise be included as a flexible endoscope having the lensbarrel 11101 of the flexible type.

The lens barrel 11101 has, at a distal end thereof, an opening in whichan objective lens is fitted. A light source apparatus 11203 is connectedto the endoscope 11100 such that light generated by the light sourceapparatus 11203 is introduced to a distal end of the lens barrel 11101by a light guide extending in the inside of the lens barrel 11101 and isirradiated toward an observation target in a body cavity of the patient11132 through the objective lens. It is to be noted that the endoscope11100 may be a forward-viewing endoscope or may be an oblique-viewingendoscope or a side-viewing endoscope.

An optical system and an imaging element are provided in the inside ofthe camera head 11102 such that reflected light (observation light) fromthe observation target is condensed on the imaging element by theoptical system. The observation light is photo-electrically converted bythe imaging element to generate an electric signal corresponding to theobservation light, namely, an image signal corresponding to anobservation image. The image signal is transmitted as RAW data to acamera control unit (CCU) 11201.

The CCU 11201 includes a central processing unit (CPU), a graphicsprocessing unit (GPU) or the like and integrally controls operation ofthe endoscope 11100 and a display apparatus 11202. Further, the CCU11201 receives an image signal from the camera head 11102 and performs,for the image signal, various image processes for displaying an imagebased on the image signal such as, for example, a development process(demosaic process).

The display apparatus 11202 displays thereon an image based on an imagesignal, for which the image processes have been performed by the CCU11201, under the control of the CCU 11201.

The light source apparatus 11203 includes a light source such as, forexample, a light emitting diode (LED) and supplies irradiation lightupon imaging of a surgical region to the endoscope 11100.

An inputting apparatus 11204 is an input interface for the endoscopicsurgery system 11000. A user can perform inputting of various kinds ofinformation or instruction inputting to the endoscopic surgery system11000 through the inputting apparatus 11204. For example, the user wouldinput an instruction or a like to change an image capturing condition(type of irradiation light, magnification, focal distance or the like)by the endoscope 11100.

A treatment tool controlling apparatus 11205 controls driving of theenergy device 11112 for cautery or incision of a tissue, sealing of ablood vessel or the like. A pneumoperitoneum apparatus 11206 feeds gasinto a body cavity of the patient 11132 through the pneumoperitoneumtube 11111 to inflate the body cavity in order to secure the field ofview of the endoscope 11100 and secure the working space for thesurgeon. A recorder 11207 is an apparatus capable of recording variouskinds of information relating to surgery. A printer 11208 is anapparatus capable of printing various kinds of information relating tosurgery in various forms such as a text, an image or a graph.

It is to be noted that the light source apparatus 11203 which suppliesirradiation light when a surgical region is to be imaged to theendoscope 11100 may include a white light source which includes, forexample, an LED, a laser light source or a combination of them. Where awhite light source includes a combination of red, green, and blue (RGB)laser light sources, since the output intensity and the output timingcan be controlled with a high degree of accuracy for each color (eachwavelength), adjustment of the white balance of a captured image can beperformed by the light source apparatus 11203. Further, in this case, iflaser beams from the respective RGB laser light sources are irradiatedtime-divisionally on an observation target and driving of the imagingelements of the camera head 11102 are controlled in synchronism with theirradiation timings. Then images individually corresponding to the R, Gand B colors can be also captured time-divisionally. According to thismethod, a color image can be obtained even if color filters are notprovided for the imaging element.

Further, the light source apparatus 11203 may be controlled such thatthe intensity of light to be outputted is changed for each predeterminedtime. By controlling driving of the imaging element of the camera head11102 in synchronism with the timing of the change of the intensity oflight to acquire images time-divisionally and synthesizing the images,an image of a high dynamic range free from underexposed blocked upshadows and overexposed highlights can be created.

Further, the light source apparatus 11203 may be configured to supplylight of a predetermined wavelength band ready for special lightobservation. In special light observation, for example, by utilizing thewavelength dependency of absorption of light in a body tissue toirradiate light of a narrow band in comparison with irradiation lightupon ordinary observation (namely, white light), narrow band observation(narrow band imaging) of imaging a predetermined tissue such as a bloodvessel of a superficial portion of the mucous membrane or the like in ahigh contrast is performed. Alternatively, in special light observation,fluorescent observation for obtaining an image from fluorescent lightgenerated by irradiation of excitation light may be performed. Influorescent observation, it is possible to perform observation offluorescent light from a body tissue by irradiating excitation light onthe body tissue (autofluorescence observation) or to obtain afluorescent light image by locally injecting a reagent such asindocyanine green (ICG) into a body tissue and irradiating excitationlight corresponding to a fluorescent light wavelength of the reagentupon the body tissue. The light source apparatus 11203 can be configuredto supply such narrow-band light and/or excitation light suitable forspecial light observation as described above.

FIG. 11 is a block diagram showing an example of a functionalconfiguration of the camera head 11102 and the CCU 11201 illustrated inFIG. 10 .

The camera head 11102 includes a lens unit 11401, an imaging unit 11402,a driving unit 11403, a communication unit 11404 and a camera headcontrolling unit 11405. The CCU 11201 includes a communication unit11411, an image processing unit 11412 and a control unit 11413. Thecamera head 11102 and the CCU 11201 are connected for communication toeach other by a transmission cable 11400.

The lens unit 11401 is an optical system, provided at a connectinglocation to the lens barrel 11101. Observation light taken in from adistal end of the lens barrel 11101 is guided to the camera head 11102and introduced into the lens unit 11401. The lens unit 11401 includes acombination of a plurality of lenses including a zoom lens and afocusing lens.

The imaging unit 11402 includes imaging elements. The number of imagingelements which is included by the imaging unit 11402 may be one(single-plate type) or a plural number (multi-plate type). Where theimaging unit 11402 is configured as that of the multi-plate type, forexample, image signals corresponding to respective R, G and B aregenerated by the imaging elements, and the image signals may besynthesized to obtain a color image. The imaging unit 11402 may also beconfigured so as to have a pair of imaging elements for acquiringrespective image signals for the right eye and the left eye ready forthree dimensional (3D) display. If 3D display is performed, then thedepth of a living body tissue in a surgical region can be comprehendedmore accurately by the surgeon 11131. It is to be noted that, where theimaging unit 11402 is configured as that of stereoscopic type, aplurality of systems of lens units 11401 are provided corresponding tothe individual imaging elements.

Further, the imaging unit 11402 may not necessarily be provided on thecamera head 11102. For example, the imaging unit 11402 may be providedimmediately behind the objective lens in the inside of the lens barrel11101.

The driving unit 11403 includes an actuator and moves the zoom lens andthe focusing lens of the lens unit 11401 by a predetermined distancealong an optical axis under the control of the camera head controllingunit 11405. Consequently, the magnification and the focal point of acaptured image by the imaging unit 11402 can be adjusted suitably.

The communication unit 11404 includes a communication apparatus fortransmitting and receiving various kinds of information to and from theCCU 11201. The communication unit 11404 transmits an image signalacquired from the imaging unit 11402 as RAW data to the CCU 11201through the transmission cable 11400.

In addition, the communication unit 11404 receives a control signal forcontrolling driving of the camera head 11102 from the CCU 11201 andsupplies the control signal to the camera head controlling unit 11405.The control signal includes information relating to image capturingconditions such as, for example, information that a frame rate of acaptured image is designated, information that an exposure value uponimage capturing is designated and/or information that a magnificationand a focal point of a captured image are designated.

It is to be noted that the image capturing conditions such as the framerate, exposure value, magnification or focal point may be designated bythe user or may be set automatically by the control unit 11413 of theCCU 11201 on the basis of an acquired image signal. In the latter case,an auto exposure (AE) function, an auto focus (AF) function and an autowhite balance (AWB) function are incorporated in the endoscope 11100.

The camera head controlling unit 11405 controls driving of the camerahead 11102 on the basis of a control signal from the CCU 11201 receivedthrough the communication unit 11404.

The communication unit 11411 includes a communication apparatus fortransmitting and receiving various kinds of information to and from thecamera head 11102. The communication unit 11411 receives an image signaltransmitted thereto from the camera head 11102 through the transmissioncable 11400.

Further, the communication unit 11411 transmits a control signal forcontrolling driving of the camera head 11102 to the camera head 11102.The image signal and the control signal can be transmitted by electricalcommunication, optical communication or the like.

The image processing unit 11412 performs various image processes for animage signal in the form of RAW data transmitted thereto from the camerahead 11102.

The control unit 11413 performs various kinds of control relating toimage capturing of a surgical region or the like by the endoscope 11100and display of a captured image obtained by image capturing of thesurgical region or the like. For example, the control unit 11413 createsa control signal for controlling driving of the camera head 11102.

Further, the control unit 11413 controls, on the basis of an imagesignal for which image processes have been performed by the imageprocessing unit 11412, the display apparatus 11202 to display a capturedimage in which the surgical region or the like is imaged. Thereupon, thecontrol unit 11413 may recognize various objects in the captured imageusing various image recognition technologies. For example, the controlunit 11413 can recognize a surgical tool such as forceps, a particularliving body region, bleeding, mist when the energy device 11112 is usedand so forth by detecting the shape, color and so forth of edges ofobjects included in a captured image. The control unit 11413 may cause,when it controls the display apparatus 11202 to display a capturedimage, various kinds of surgery supporting information to be displayedin an overlapping manner with an image of the surgical region using aresult of the recognition. Where surgery supporting information isdisplayed in an overlapping manner and presented to the surgeon 11131,the burden on the surgeon 11131 can be reduced and the surgeon 11131 canproceed with the surgery with certainty.

The transmission cable 11400 which connects the camera head 11102 andthe CCU 11201 to each other is an electric signal cable ready forcommunication of an electric signal, an optical fiber ready for opticalcommunication or a composite cable ready for both of electrical andoptical communications.

Here, while, in the example illustrated, communication is performed bywired communication using the transmission cable 11400, thecommunication between the camera head 11102 and the CCU 11201 may beperformed by wireless communication.

Hereinabove, an example of an endoscopic surgery system to which thetechnology according to the present disclosure can be applied isdescribed. The technology according to the present disclosure can beapplied to, of the configuration described above, the endoscope 11100,(the imaging unit 11402 of) the camera head 11102, or the like.Specifically, the solid-state imaging element according to the presenttechnology can be used for the imaging unit 10402. By applying thetechnology according to the present disclosure to the endoscope 11100,(the imaging unit 11402 of) the camera head 11102, or the like, clearerimage of a surgical region can be obtained, for example, and thus asurgeon can confirm the surgical region with certainty.

Note that, although the endoscopic surgery system has been described asan example herein, the technology according to the present disclosure(the present technology) may also be applied to others, for example, amicroscope surgery system, and the like.

8. Application Example to Mobile Bodies

The technology according to the present disclosure (present technology)can be applied to various products. For example, the technologyaccording to the present disclosure may be implemented as apparatusesmounted on any type of mobile bodies such as automobiles, electricvehicles, hybrid electric vehicles, motorcycles, bicycles, personalmobilities, airplanes, drones, ships, and robots.

FIG. 12 is a block diagram showing an example of schematic configurationof a vehicle control system as an example of a mobile body controlsystem to which the technology according to an embodiment of the presentdisclosure can be applied.

The vehicle control system 12000 includes a plurality of electroniccontrol units connected to each other via a communication network 12001.In the example illustrated in FIG. 12 , the vehicle control system 12000includes a driving system control unit 12010, a body system control unit12020, an outside-vehicle information detecting unit 12030, anin-vehicle information detecting unit 12040, and an integrated controlunit 12050. In addition, a microcomputer 12051, a sound/image outputsection 12052, and a vehicle-mounted network interface (I/F) 12053 areillustrated as a functional configuration of the integrated control unit12050.

The driving system control unit 12010 controls the operation of devicesrelated to the driving system of the vehicle in accordance with variouskinds of programs. For example, the driving system control unit 12010functions as a control device for a driving force generating device forgenerating the driving force of the vehicle, such as an internalcombustion engine, a driving motor, or the like, a driving forcetransmitting mechanism for transmitting the driving force to wheels, asteering mechanism for adjusting the steering angle of the vehicle, abraking device for generating the braking force of the vehicle, and thelike.

The body system control unit 12020 controls the operation of variouskinds of devices provided to a vehicle body in accordance with variouskinds of programs. For example, the body system control unit 12020functions as a control device for a keyless entry system, a smart keysystem, a power window device, or various kinds of lamps such as aheadlamp, a backup lamp, a brake lamp, a turn signal, a fog lamp, or thelike. In this case, radio waves transmitted from a mobile device as analternative to a key or signals of various kinds of switches can beinput to the body system control unit 12020. The body system controlunit 12020 receives these input radio waves or signals, and controls adoor lock device, the power window device, the lamps, or the like of thevehicle.

The outside-vehicle information detecting unit 12030 detects informationabout the outside of the vehicle including the vehicle control system12000. For example, the outside-vehicle information detecting unit 12030is connected with an imaging unit 12031. The outside-vehicle informationdetecting unit 12030 makes the imaging unit 12031 image an image of theoutside of the vehicle, and receives the imaged image. On the basis ofthe received image, the outside-vehicle information detecting unit 12030may perform processing of detecting an object such as a human, avehicle, an obstacle, a sign, a character on a road surface, or thelike, or processing of detecting a distance thereto.

The imaging unit 12031 is an optical sensor that receives light, andwhich outputs an electric signal corresponding to a received lightamount of the light. The imaging unit 12031 can output the electricsignal as an image, or can output the electric signal as informationabout a measured distance. In addition, the light received by theimaging unit 12031 may be visible light, or may be invisible light suchas infrared rays or the like.

The in-vehicle information detecting unit 12040 detects informationabout the inside of the vehicle. The in-vehicle information detectingunit 12040 is, for example, connected with a driver state detectingsection 12041 that detects the state of a driver. The driver statedetecting section 12041, for example, includes a camera that images thedriver. On the basis of detection information input from the driverstate detecting section 12041, the in-vehicle information detecting unit12040 may calculate a degree of fatigue of the driver or a degree ofconcentration of the driver, or may determine whether the driver isdozing.

The microcomputer 12051 can calculate a control target value for thedriving force generating device, the steering mechanism, or the brakingdevice on the basis of the information about the inside or outside ofthe vehicle which information is obtained by the outside-vehicleinformation detecting unit 12030 or the in-vehicle information detectingunit 12040, and output a control command to the driving system controlunit 12010. For example, the microcomputer 12051 can perform cooperativecontrol intended to implement functions of an advanced driver assistancesystem (ADAS) which functions include collision avoidance or shockmitigation for the vehicle, following driving based on a followingdistance, vehicle speed maintaining driving, a warning of collision ofthe vehicle, a warning of deviation of the vehicle from a lane, or thelike.

In addition, the microcomputer 12051 can perform cooperative controlintended for automatic driving, which makes the vehicle to travelautonomously without depending on the operation of the driver, or thelike, by controlling the driving force generating device, the steeringmechanism, the braking device, or the like on the basis of theinformation about the outside or inside of the vehicle which informationis obtained by the outside-vehicle information detecting unit 12030 orthe in-vehicle information detecting unit 12040.

In addition, the microcomputer 12051 can output a control command to thebody system control unit 12020 on the basis of the information about theoutside of the vehicle which information is obtained by theoutside-vehicle information detecting unit 12030. For example, themicrocomputer 12051 can perform cooperative control intended to preventa glare by controlling the headlamp so as to change from a high beam toa low beam, for example, in accordance with the position of a precedingvehicle or an oncoming vehicle detected by the outside-vehicleinformation detecting unit 12030.

The sound/image output section 12052 transmits an output signal of atleast one of a sound or an image to an output device capable of visuallyor auditorily notifying information to an occupant of the vehicle or theoutside of the vehicle. In the example of FIG. 12 , an audio speaker12061, a display section 12062, and an instrument panel 12063 areillustrated as the output device. The display section 12062 may, forexample, include at least one of an on-board display or a head-updisplay.

FIG. 13 is a diagram showing an example of the installation position ofthe imaging unit 12031.

In FIG. 13 , the vehicle 12100 includes imaging units 12101, 12102,12103, 12104, and 12105 as the imaging unit 12031.

The imaging units 12101, 12102, 12103, 12104, and 12105 are, forexample, disposed at positions on a front nose, sideview mirrors, a rearbumper, and a back door of the vehicle 12100 as well as a position on anupper portion of a windshield within the interior of the vehicle. Theimaging unit 12101 provided to the front nose and the imaging unit 12105provided to the upper portion of the windshield within the interior ofthe vehicle obtain mainly an image of the front of the vehicle 12100.The imaging units 12102 and 12103 provided to the sideview mirrorsobtain mainly an image of the sides of the vehicle 12100. The imagingunit 12104 provided to the rear bumper or the back door obtains mainlyan image of the rear of the vehicle 12100. The imaging units 12101 and12105 provided to the upper portion of the windshield within theinterior of the vehicle is used mainly to detect a preceding vehicle, apedestrian, an obstacle, a signal, a traffic sign, a lane, or the like.

Incidentally, FIG. 13 illustrates an example of imaging ranges of theimaging units 12101 to 12104. An imaging range 12111 represents theimaging range of the imaging unit 12101 provided to the front nose.Imaging ranges 12112 and 12113 respectively represent the imaging rangesof the imaging units 12102 and 12103 provided to the sideview mirrors.An imaging range 12114 represents the imaging range of the imaging unit12104 provided to the rear bumper or the back door. A bird's-eye imageof the vehicle 12100 as viewed from above is obtained by superimposingimage data imaged by the imaging units 12101 to 12104, for example.

At least one of the imaging units 12101 to 12104 may have a function ofobtaining distance information. For example, at least one of the imagingunits 12101 to 12104 may be a stereo camera constituted of a pluralityof imaging elements, or may be an imaging element having pixels forphase difference detection.

For example, the microcomputer 12051 can determine a distance to eachthree-dimensional object within the imaging ranges 12111 to 12114 and atemporal change in the distance (relative speed with respect to thevehicle 12100) on the basis of the distance information obtained fromthe imaging units 12101 to 12104, and thereby extract, as a precedingvehicle, a nearest three-dimensional object in particular that ispresent on a traveling path of the vehicle 12100 and which travels insubstantially the same direction as the vehicle 12100 at a predeterminedspeed (for example, equal to or more than 0 km/hour). Further, themicrocomputer 12051 can set a following distance to be maintained infront of a preceding vehicle in advance, and perform automatic brakecontrol (including following stop control), automatic accelerationcontrol (including following start control), or the like. It is thuspossible to perform cooperative control intended for automatic drivingthat makes the vehicle travel autonomously without depending on theoperation of the driver or the like.

For example, the microcomputer 12051 can classify three-dimensionalobject data on three-dimensional objects into three-dimensional objectdata of a two-wheeled vehicle, a standard-sized vehicle, a large-sizedvehicle, a pedestrian, a utility pole, and other three-dimensionalobjects on the basis of the distance information obtained from theimaging units 12101 to 12104, extract the classified three-dimensionalobject data, and use the extracted three-dimensional object data forautomatic avoidance of an obstacle. For example, the microcomputer 12051identifies obstacles around the vehicle 12100 as obstacles that thedriver of the vehicle 12100 can recognize visually and obstacles thatare difficult for the driver of the vehicle 12100 to recognize visually.Then, the microcomputer 12051 determines a collision risk indicating arisk of collision with each obstacle. In a situation in which thecollision risk is equal to or higher than a set value and there is thusa possibility of collision, the microcomputer 12051 outputs a warning tothe driver via the audio speaker 12061 or the display section 12062, andperforms forced deceleration or avoidance steering via the drivingsystem control unit 12010. The microcomputer 12051 can thereby assist indriving to avoid collision.

At least one of the imaging units 12101 to 12104 may be an infraredcamera that detects infrared rays. The microcomputer 12051 can, forexample, recognize a pedestrian by determining whether or not there is apedestrian in captured images of the imaging units 12101 to 12104. Suchrecognition of a pedestrian is, for example, performed by a procedure ofextracting characteristic points in the captured images of the imagingunits 12101 to 12104 as infrared cameras and a procedure of determiningwhether or not it is the pedestrian by performing pattern matchingprocessing on a series of characteristic points representing the contourof the object. When the microcomputer 12051 determines that there is apedestrian in the captured images of the imaging units 12101 to 12104,and thus recognizes the pedestrian, the sound/image output section 12052controls the display section 12062 so that a square contour line foremphasis is displayed so as to be superimposed on the recognizedpedestrian. Furthermore, the sound/image output section 12052 may alsocontrol the display section 12062 so that an icon or the likerepresenting the pedestrian is displayed at a desired position.

Hereinabove, an example of a vehicle control system to which thetechnology according to the present disclosure (present technology) canbe applied is described. The technology according to the presentdisclosure can be applied to, of the configuration described above, forexample, the imaging unit 12031 or the like. Specifically, thesolid-state imaging element according to the present technology can beused for the imaging unit 12031. Easier-to-see captured images can beobtained by applying the technology according to the present disclosureto the imaging unit 12031, and therefore the fatigue of the driver canbe reduced.

EXAMPLES

Hereinbelow, the present technology is described more specifically byusing Examples; however, the present technology is not limited to thefollowing Examples, to the extent of the gist of the present technology.

Example 1 Experiment 1-1

First, a second oxide semiconductor layer is produced.

A material such as IGZO may be used to produce the second oxidesemiconductor layer.

-   -   A vacuum sputtering method using an IGZO material as a target is        used as a method for forming an IGZO film.    -   Before the film formation by sputtering, preheating is performed        in a room connected to a sputtering chamber through a vacuum        conveyance chamber. Adsorbed water of a substrate is eliminated        by the preheating. It is desirable that the ultimate vacuum of        the preheating chamber be not more than the level of 3×10⁻⁵ Pa,        the heating temperature be 250° C., and the treatment time be        not less than 1 min.    -   After the preheating, the workpiece is conveyed to the        sputtering chamber by vacuum conveyance.    -   It is desirable that the degree of vacuum of the sputtering        chamber be not more than 3×10⁻⁵ Pa and the distance between the        target and the substrate (a TS distance) be 70 to 200 mm. For        film formation conditions, Ar gas and oxygen gas are introduced,        and the flow rate of Ar gas is set to 50 to 200 sccm and the        flow rate of oxygen gas is to 2 to 50 sccm. It is desirable that        the gas pressure be 0.2 to 0.5 Pa and the film formation        temperature be in the range of room temperature to 300° C. The        sputtering discharge may be either of a direct current (DC)        magnetron method and an RF magnetron sputtering method using        radio frequency.    -   The parameters of pressure, power, and film formation        temperature are adjusted so that the film density after film        formation is in the range of 5.90 to 6.15 g/cm³. The film        density is found by fitting of a waveform obtained by reflected        X-ray intensity measurement.    -   The film thickness of the second oxide semiconductor layer is        adjusted so as to be, for example, 30 to 50 nm.    -   Next, annealing is performed in a water vapor atmosphere in        order to reduce the number of traps.    -   The annealing in a water vapor atmosphere is performed at        atmospheric pressure and in a range of water concentration of 20        to 50%. It is desirable that the annealing temperature be not        less than 300° C. and the treatment time be not less than 1        hour. SIMS analysis is performed to make the quantitative        measurement of hydrogen concentration in the IGZO film after        annealing. The hydrogen concentration in the IGZO film (in the        second oxide semiconductor layer) is adjusted so as to be, for        example, not less than 1.0E20 atoms/cm² in the entire region of        the film thickness.

Experiment 1-2

Next, a first oxide semiconductor layer-1 is produced on the secondoxide semiconductor layer.

-   -   A material such as IGZO may be used to produce the first oxide        semiconductor layer.    -   A vacuum sputtering method using an IGZO material as a target is        used as a method for forming an IGZO film, like for the second        oxide semiconductor layer.    -   It is desirable that the degree of vacuum of the sputtering        chamber be not more than 3×10⁻⁵ Pa and the distance between the        target and the substrate (a TS distance) be 70 to 200 mm. For        film formation conditions, Ar gas and oxygen gas are introduced,        and the flow rate of Ar gas is set to 50 to 200 sccm and the        flow rate of oxygen gas is to 10 to 50 sccm in order to form a        high density IGZO film layer. It is desirable that the gas        pressure be 0.2 to 0.5 Pa and the film formation temperature be        in the range of room temperature to 300° C. The sputtering        discharge may be either of a direct current (DC) magnetron        method and an RF magnetron sputtering method using radio        frequency.    -   The film density of the first oxide semiconductor layer-1 is        adjusted so as to be higher than the film density of the second        oxide semiconductor layer, and is adjusted so as to be, for        example, 6.20 g/cm³.    -   The film thickness of the first oxide semiconductor layer-1,        which is a high density layer, is adjusted so as to be, for        example, not less than 5 nm and less than 30 nm.

Experiment 1-3

A photoelectric conversion layer is formed on the first oxidesemiconductor layer-1, and then a first electrode (an upper electrode)is formed on the photoelectric conversion layer. Further, a secondelectrode (a lower electrode) is formed under the second oxidesemiconductor layer, and then a semiconductor substrate in which aphotoelectric conversion section (for example, an inorganicphotoelectric conversion section containing an inorganic-based material)is formed is stacked below the second electrode. Finally, functionalelements such as a memory element are provided, and a wiring layer isformed on the front surface side (the surface side on which thephotoelectric conversion layer is not formed) of the semiconductorsubstrate; thus, a solid-state imaging element-1 is manufactured. Notethat the photoelectric conversion layer formed on the first oxidesemiconductor layer-1 may be an organic semiconductor layer or may be alayer containing an inorganic material as a main component. Further, ap-type buffer layer containing an organic-based material or aninorganic-based material may be formed between the first electrode andthe photoelectric conversion layer, and an n-type buffer layercontaining an organic-based material or an inorganic-based material maybe formed between the photoelectric conversion layer and the first oxidesemiconductor layer-1.

Example 2 Experiment 2-1

First, a second oxide semiconductor layer is produced in conformity withthe method of experiment 1-1 above.

Experiment 2-2

Next, a first oxide semiconductor layer-2 that is a low hydrogenconcentration layer is produced on the second oxide semiconductor layer.

-   -   In order to reduce the hydrogen concentration in the film, it is        desirable that the ultimate vacuum of the film formation chamber        be set to not more than 1×10⁻⁵ Pa or not more than 5×10⁻⁶ Pa.

Experiment 2-3

A photoelectric conversion layer is formed on the first oxidesemiconductor layer-2, and then a first electrode (an upper electrode)is formed on the photoelectric conversion layer. Further, a secondelectrode (a lower electrode) is formed under the second oxidesemiconductor layer, and then a semiconductor substrate in which aphotoelectric conversion section (for example, an inorganicphotoelectric conversion section containing an inorganic-based material)is formed is stacked below the second electrode. Finally, functionalelements such as a memory element are provided, and a wiring layer isformed on the front surface side (the surface side on which thephotoelectric conversion layer is not formed) of the semiconductorsubstrate; thus, a solid-state imaging element-2 is manufactured. Notethat the photoelectric conversion layer formed on the first oxidesemiconductor layer-2 may be an organic semiconductor layer or may be alayer containing an inorganic material as a main component. Further, ap-type buffer layer containing an organic-based material or aninorganic-based material may be formed between the first electrode andthe photoelectric conversion layer, and an n-type buffer layercontaining an organic-based material or an inorganic-based material maybe formed between the photoelectric conversion layer and the first oxidesemiconductor layer-2.

Example 3 Experiment 3-1

First, a second oxide semiconductor layer is produced in conformity withthe method of experiment 1-1 above.

Experiment 3-2

Next, a first oxide semiconductor layer-3 that is a high density layerand is also a low hydrogen concentration layer is produced on the secondoxide semiconductor layer.

-   -   The film formation conditions are similar to the film formation        conditions of the first oxide semiconductor layer-1, which is a        high density layer, produced in experiment 1-2 above; however,        in order to reduce the hydrogen concentration in the film, it is        desirable that the ultimate vacuum of the film formation chamber        be set to not more than 1×10⁻⁵ Pa or not more than 5×10⁻⁶ Pa.

Experiment 3-3

A photoelectric conversion layer is formed on the first oxidesemiconductor layer-3, and then a first electrode (an upper electrode)is formed on the photoelectric conversion layer. Further, a secondelectrode (a lower electrode) is formed under the second oxidesemiconductor layer, and then a semiconductor substrate in which aphotoelectric conversion section (for example, an inorganicphotoelectric conversion section containing an inorganic-based material)is formed is stacked below the second electrode. Finally, functionalelements such as a memory element are provided, and a wiring layer isformed on the front surface side (the surface side on which thephotoelectric conversion layer is not formed) of the semiconductorsubstrate; thus, a solid-state imaging element-3 is manufactured. Notethat the photoelectric conversion layer formed on the first oxidesemiconductor layer-3 may be an organic semiconductor layer or may be alayer containing an inorganic material as a main component. Further, ap-type buffer layer containing an organic-based material or aninorganic-based material may be formed between the first electrode andthe photoelectric conversion layer, and an n-type buffer layercontaining an organic-based material or an inorganic-based material maybe formed between the photoelectric conversion layer and the first oxidesemiconductor layer-3.

Hereinabove, a description is given using embodiments, use examples,application examples, and Examples; however, the subject matter of thepresent technology is not limited to the above embodiments, the aboveuse examples, the above application examples, or the above Examples, butcan be variously modified.

Further, although the above embodiments are described using, as anexample, a configuration of a back-side illumination solid-state imagingelement, the above embodiments can be applied also to a front-sideillumination solid-state imaging element.

Furthermore, the effects described in the present specification are onlyexamples and are not limitative ones, and there may be other effects.

Additionally, the present technology may also be configured as below.

[1]

A solid-state imaging element including at least: a first photoelectricconversion section; and a semiconductor substrate in which a secondphotoelectric conversion section is formed, in this order from a lightincidence side, in which

the first photoelectric conversion section includes at least a firstelectrode, a photoelectric conversion layer, a first oxide semiconductorlayer, a second oxide semiconductor layer, and a second electrode inthis order, and

a film density of the first oxide semiconductor layer is higher than afilm density of the second oxide semiconductor layer.

[2]

The solid-state imaging element according to [1], in which a hydrogenconcentration of the first oxide semiconductor layer is lower than ahydrogen concentration of the second oxide semiconductor layer.

[3]

The solid-state imaging element according to [1] or [2], in which thephotoelectric conversion layer contains at least one organicsemiconductor material.

[4]

The solid-state imaging element according to any one of [1] to [3], inwhich the first photoelectric conversion section further includes ann-type buffer layer between the photoelectric conversion layer and thefirst oxide semiconductor layer.

[5]

The solid-state imaging element according to any one of [1] to [3], inwhich the first photoelectric conversion section further includes ap-type buffer layer between the first electrode and the photoelectricconversion layer.

[6]

The solid-state imaging element according to any one of [1] to [3], inwhich

the first photoelectric conversion section further includes an n-typebuffer layer between the photoelectric conversion layer and the firstoxide semiconductor layer, and

the first photoelectric conversion section further includes a p-typebuffer layer between the first electrode and the photoelectricconversion layer.

[7]

A solid-state imaging element including at least: a first photoelectricconversion section; and a semiconductor substrate in which a secondphotoelectric conversion section is formed, in this order from a lightincidence side, in which

the first photoelectric conversion section includes at least a firstelectrode, a photoelectric conversion layer, a first oxide semiconductorlayer, a second oxide semiconductor layer, and a second electrode inthis order, and

a hydrogen concentration of the first oxide semiconductor layer is lowerthan a hydrogen concentration of the second oxide semiconductor layer.

[8]

The solid-state imaging element according to [7], in which a filmdensity of the first oxide semiconductor layer is higher than a filmdensity of the second oxide semiconductor layer.

[9]

The solid-state imaging element according to [7] or [8], in which thephotoelectric conversion layer contains at least one organicsemiconductor material.

[10]

The solid-state imaging element according to any one of [7] to [9], inwhich the first photoelectric conversion section further includes ann-type buffer layer between the photoelectric conversion layer and thefirst oxide semiconductor layer.

[11]

The solid-state imaging element according to any one of [7] to [9], inwhich the first photoelectric conversion section further includes ap-type buffer layer between the first electrode and the photoelectricconversion layer.

[12]

The solid-state imaging element according to any one of [7] to [9], inwhich

the first photoelectric conversion section further includes an n-typebuffer layer between the photoelectric conversion layer and the firstoxide semiconductor layer, and

the first photoelectric conversion section further includes a p-typebuffer layer between the first electrode and the photoelectricconversion layer.

[13]

A solid-state imaging element including at least: a first photoelectricconversion section; and a semiconductor substrate in which a secondphotoelectric conversion section is formed, in this order from a lightincidence side, in which

the first photoelectric conversion section includes at least a firstelectrode, a photoelectric conversion layer, a first oxide semiconductorlayer, a second oxide semiconductor layer, and a second electrode inthis order,

a film density of the first oxide semiconductor layer is higher than afilm density of the second oxide semiconductor layer, and

a hydrogen concentration of the first oxide semiconductor layer is lowerthan a hydrogen concentration of the second oxide semiconductor layer.

[14]

The solid-state imaging element according to [13], in which thephotoelectric conversion layer contains at least one organicsemiconductor material.

[15]

The solid-state imaging element according to [13] or [14], in which thefirst photoelectric conversion section further includes an n-type bufferlayer between the photoelectric conversion layer and the first oxidesemiconductor layer.

[16]

The solid-state imaging element according to [13] or [14], in which thefirst photoelectric conversion section further includes a p-type bufferlayer between the first electrode and the photoelectric conversionlayer.

[17]

The solid-state imaging element according to [13] or [14], in which

the first photoelectric conversion section further includes an n-typebuffer layer between the photoelectric conversion layer and the firstoxide semiconductor layer, and

the first photoelectric conversion section further includes a p-typebuffer layer between the first electrode and the photoelectricconversion layer.

[18]

An electronic device including the solid-state imaging element accordingto any one of [1] to [17].

REFERENCE SIGNS LIST

-   10 Solid-state imaging element-   10A First photoelectric conversion section-   11 Second electrode-   12 Insulating layer-   13 Second oxide semiconductor layer-   14 First oxide semiconductor layer-   15 Photoelectric conversion layer-   16 First electrode-   17 p-type buffer layer-   18 n-type buffer layer-   30 Semiconductor substrate

What is claimed is:
 1. A solid-state imaging element, comprising: afirst photoelectric conversion section, wherein the first photoelectricconversion section includes at least a first electrode, a photoelectricconversion layer, a first oxide semiconductor layer, a second oxidesemiconductor layer, and a second electrode in this order, and wherein afilm density of the first oxide semiconductor layer is higher than afilm density of the second oxide semiconductor layer.
 2. The solid-stateimaging element according to claim 1, further comprising a semiconductorsubstrate in which a second photoelectric conversion section is formed,wherein the solid-state imaging element comprises the firstphotoelectric conversion section and the semiconductor substrate in thisorder from a light incident side of the solid-state imaging element. 3.The solid-state imaging element according to claim 1, wherein a hydrogenconcentration of the first oxide semiconductor layer is lower than ahydrogen concentration of the second oxide semiconductor layer.
 4. Thesolid-state imaging element according to claim 1, wherein thephotoelectric conversion layer contains at least one organicsemiconductor material.
 5. The solid-state imaging element according toclaim 1, wherein the first photoelectric conversion section furtherincludes an n-type buffer layer between the photoelectric conversionlayer and the first oxide semiconductor layer.
 6. The solid-stateimaging element according to claim 1, wherein the first photoelectricconversion section further includes a p-type buffer layer between thefirst electrode and the photoelectric conversion layer.
 7. Thesolid-state imaging element according to claim 1, wherein the firstphotoelectric conversion section further includes an n-type buffer layerbetween the photoelectric conversion layer and the first oxidesemiconductor layer, and wherein the first photoelectric conversionsection further includes a p-type buffer layer between the firstelectrode and the photoelectric conversion layer.
 8. A solid-stateimaging element, comprising: a first photoelectric conversion section,wherein the first photoelectric conversion section includes at least afirst electrode, a photoelectric conversion layer, a first oxidesemiconductor layer, a second oxide semiconductor layer, and a secondelectrode in this order, and wherein a hydrogen concentration of thefirst oxide semiconductor layer is lower than a hydrogen concentrationof the second oxide semiconductor layer.
 9. The solid-state imagingelement according to claim 8, further comprising a semiconductorsubstrate in which a second photoelectric conversion section is formed,wherein the solid-state imaging element comprises the firstphotoelectric conversion section and the semiconductor substrate in thisorder from a light incident side of the solid-state imaging element. 10.The solid-state imaging element according to claim 9, wherein a filmdensity of the first oxide semiconductor layer is higher than a filmdensity of the second oxide semiconductor layer.
 11. The solid-stateimaging element according to claim 8, wherein the photoelectricconversion layer contains at least one organic semiconductor material.12. The solid-state imaging element according to claim 8, wherein thefirst photoelectric conversion section further includes an n-type bufferlayer between the photoelectric conversion layer and the first oxidesemiconductor layer.
 13. The solid-state imaging element according toclaim 8, wherein the first photoelectric conversion section furtherincludes a p-type buffer layer between the first electrode and thephotoelectric conversion layer.
 14. The solid-state imaging elementaccording to claim 8, wherein the first photoelectric conversion sectionfurther includes an n-type buffer layer between the photoelectricconversion layer and the first oxide semiconductor layer, and whereinthe first photoelectric conversion section further includes a p-typebuffer layer between the first electrode and the photoelectricconversion layer.
 15. A solid-state imaging element, comprising: a firstphotoelectric conversion section; and a semiconductor substrate in whicha second photoelectric conversion section is formed, wherein the firstphotoelectric conversion section includes at least a first electrode, aphotoelectric conversion layer, a first oxide semiconductor layer, asecond oxide semiconductor layer, and a second electrode in this order,wherein a film density of the first oxide semiconductor layer is higherthan a film density of the second oxide semiconductor layer, wherein ahydrogen concentration of the first oxide semiconductor layer is lowerthan a hydrogen concentration of the second oxide semiconductor layer.16. The solid-state imaging element according to claim 15, wherein thesolid-state imaging element comprises the first photoelectric conversionsection and the semiconductor substrate in this order from a lightincident side of the solid-state imaging element.
 17. The solid-stateimaging element according to claim 15, wherein the photoelectricconversion layer contains at least one organic semiconductor material.18. The solid-state imaging element according to claim 15, wherein thefirst photoelectric conversion section further includes an n-type bufferlayer between the photoelectric conversion layer and the first oxidesemiconductor layer.
 19. The solid-state imaging element according toclaim 15, wherein the first photoelectric conversion section furtherincludes a p-type buffer layer between the first electrode and thephotoelectric conversion layer.
 20. The solid-state imaging elementaccording to claim 15, wherein the first photoelectric conversionsection further includes an n-type buffer layer between thephotoelectric conversion layer and the first oxide semiconductor layer,and wherein the first photoelectric conversion section further includesa p-type buffer layer between the first electrode and the photoelectricconversion layer.